How effective is the patch at preventing pregnancy?

The patch can be very effective—but only when it’s changed on time. With perfect use, the patch is more than 99% effective. Typical use is far more likely, however, and that’s around 91%.

In other words:

Of those women who use the patch exactly as directed, fewer than 1 in 100 will experience an accidental pregnancy during the first year of using this method.

Of those women who do not use the patch exactly as directed, about 9 in 100 will experience an accidental pregnancy during the first year of using this method.